/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id$
 */
package wx.xml.xalan.xpath.axes;

import wx.xml.xalan.xml.dtm.Axis;
import wx.xml.xalan.xml.dtm.DTM;
import wx.xml.xalan.xml.dtm.DTMIterator;
import wx.xml.xalan.xpath.Expression;
import wx.xml.xalan.xpath.ExpressionOwner;
import wx.xml.xalan.xpath.XPathVisitor;
import wx.xml.xalan.xpath.compiler.Compiler;
import wx.xml.xalan.xpath.compiler.OpCodes;
import wx.xml.xalan.xpath.compiler.OpMap;

/**
 * This class extends NodeSetDTM, which implements DTMIterator,
 * and fetches nodes one at a time in document order based on a XPath
 * <a href="http://www.w3.org/TR/xpath#NT-UnionExpr">UnionExpr</a>.
 * As each node is iterated via nextNode(), the node is also stored
 * in the NodeVector, so that previousNode() can easily be done.
 *
 * @xsl.usage advanced
 */
public class UnionPathIterator extends LocPathIterator
    implements Cloneable, DTMIterator, java.io.Serializable, PathComponent {
    static final long serialVersionUID = -3910351546843826781L;
    /**
     * The location path iterators, one for each
     * <a href="http://www.w3.org/TR/xpath#NT-LocationPath">location
     * path</a> contained in the union expression.
     *
     * @serial
     */
    protected LocPathIterator[] m_exprs;
    /**
     * The location path iterators, one for each
     * <a href="http://www.w3.org/TR/xpath#NT-LocationPath">location
     * path</a> contained in the union expression.
     *
     * @serial
     */
    protected DTMIterator[] m_iterators;

    /**
     * Constructor to create an instance which you can add location paths to.
     */
    public UnionPathIterator() {

        super();

        // m_mutable = false;
        // m_cacheNodes = false;
        m_iterators = null;
        m_exprs = null;
    }

    /**
     * Create a UnionPathIterator object, including creation
     * of location path iterators from the opcode list, and call back
     * into the Compiler to create predicate expressions.
     *
     * @param compiler The Compiler which is creating
     *                 this expression.
     * @param opPos    The position of this iterator in the
     *                 opcode list from the compiler.
     * @throws javax.xml.transform.TransformerException
     */
    public UnionPathIterator(Compiler compiler, int opPos)
        throws javax.xml.transform.TransformerException {

        super();

        opPos = OpMap.getFirstChildPos(opPos);

        loadLocationPaths(compiler, opPos, 0);
    }

    /**
     * This will return an iterator capable of handling the union of paths given.
     *
     * @param compiler The Compiler which is creating
     *                 this expression.
     * @param opPos    The position of this iterator in the
     *                 opcode list from the compiler.
     * @return Object that is derived from LocPathIterator.
     * @throws javax.xml.transform.TransformerException
     */
    public static LocPathIterator createUnionIterator(Compiler compiler, int opPos)
        throws javax.xml.transform.TransformerException {
        // For the moment, I'm going to first create a full UnionPathIterator, and
        // then see if I can reduce it to a UnionChildIterator.  It would obviously
        // be more effecient to just test for the conditions for a UnionChildIterator,
        // and then create that directly.
        UnionPathIterator upi                 = new UnionPathIterator(compiler, opPos);
        int               nPaths              = upi.m_exprs.length;
        boolean           isAllChildIterators = true;
        for (int i = 0; i < nPaths; i++) {
            LocPathIterator lpi = upi.m_exprs[i];

            if (lpi.getAxis() != Axis.CHILD) {
                isAllChildIterators = false;
                break;
            } else {
                // check for positional predicates or position function, which won't work.
                if (HasPositionalPredChecker.check(lpi)) {
                    isAllChildIterators = false;
                    break;
                }
            }
        }
        if (isAllChildIterators) {
            UnionChildIterator uci = new UnionChildIterator();

            for (int i = 0; i < nPaths; i++) {
                PredicatedNodeTest lpi = upi.m_exprs[i];
                // I could strip the lpi down to a pure PredicatedNodeTest, but
                // I don't think it's worth it.  Note that the test can be used
                // as a static object... so it doesn't have to be cloned.
                uci.addNodeTest(lpi);
            }
            return uci;

        } else
            return upi;
    }

    /**
     * Initialize the context values for this expression
     * after it is cloned.
     *
     * @param context The XPath runtime context for this
     *                transformation.
     */
    public void setRoot(int context, Object environment) {
        super.setRoot(context, environment);

        try {
            if (null != m_exprs) {
                int         n          = m_exprs.length;
                DTMIterator newIters[] = new DTMIterator[n];

                for (int i = 0; i < n; i++) {
                    DTMIterator iter = m_exprs[i].asIterator(m_execContext, context);
                    newIters[i] = iter;
                    iter.nextNode();
                }
                m_iterators = newIters;
            }
        } catch (Exception e) {
            throw new wx.xml.xalan.xml.utils.WrappedRuntimeException(e);
        }
    }

    /**
     * Add an iterator to the union list.
     *
     * @param expr non-null reference to a location path iterator.
     */
    public void addIterator(DTMIterator expr) {

        // Increase array size by only 1 at a time.  Fix this
        // if it looks to be a problem.
        if (null == m_iterators) {
            m_iterators = new DTMIterator[1];
            m_iterators[0] = expr;
        } else {
            DTMIterator[] exprs = m_iterators;
            int           len   = m_iterators.length;

            m_iterators = new DTMIterator[len + 1];

            System.arraycopy(exprs, 0, m_iterators, 0, len);

            m_iterators[len] = expr;
        }
        expr.nextNode();
        if (expr instanceof Expression)
            ((Expression) expr).exprSetParent(this);
    }

    /**
     * Detaches the iterator from the set which it iterated over, releasing
     * any computational resources and placing the iterator in the INVALID
     * state. After<code>detach</code> has been invoked, calls to
     * <code>nextNode</code> or<code>previousNode</code> will raise the
     * exception INVALID_STATE_ERR.
     */
    public void detach() {
        if (m_allowDetach && null != m_iterators) {
            int n = m_iterators.length;
            for (int i = 0; i < n; i++) {
                m_iterators[i].detach();
            }
            m_iterators = null;
        }
    }

    /**
     * Get the analysis bits for this walker, as defined in the WalkerFactory.
     *
     * @return One of WalkerFactory#BIT_DESCENDANT, etc.
     */
    public int getAnalysisBits() {
        int bits = 0;

        if (m_exprs != null) {
            int n = m_exprs.length;

            for (int i = 0; i < n; i++) {
                int bit = m_exprs[i].getAnalysisBits();
                bits |= bit;
            }
        }

        return bits;
    }

    /**
     * Read the object from a serialization stream.
     *
     * @param stream Input stream to read from
     * @throws java.io.IOException
     * @throws javax.xml.transform.TransformerException
     */
    private void readObject(java.io.ObjectInputStream stream)
        throws java.io.IOException, javax.xml.transform.TransformerException {
        try {
            stream.defaultReadObject();
            m_clones = new IteratorPool(this);
        } catch (ClassNotFoundException cnfe) {
            throw new javax.xml.transform.TransformerException(cnfe);
        }
    }

    /**
     * Get a cloned LocPathIterator that holds the same
     * position as this iterator.
     *
     * @return A clone of this iterator that holds the same node position.
     * @throws CloneNotSupportedException
     */
    public Object clone() throws CloneNotSupportedException {

        UnionPathIterator clone = (UnionPathIterator) super.clone();
        if (m_iterators != null) {
            int n = m_iterators.length;

            clone.m_iterators = new DTMIterator[n];

            for (int i = 0; i < n; i++) {
                clone.m_iterators[i] = (DTMIterator) m_iterators[i].clone();
            }
        }

        return clone;
    }

    /**
     * Create a new location path iterator.
     *
     * @param compiler The Compiler which is creating
     *                 this expression.
     * @param opPos    The position of this iterator in the
     * @return New location path iterator.
     * @throws javax.xml.transform.TransformerException
     */
    protected LocPathIterator createDTMIterator(
        Compiler compiler, int opPos) throws javax.xml.transform.TransformerException {
        LocPathIterator lpi = (LocPathIterator) WalkerFactory.newDTMIterator(compiler, opPos,
            (compiler.getLocationPathDepth() <= 0));
        return lpi;
    }

    /**
     * Initialize the location path iterators.  Recursive.
     *
     * @param compiler The Compiler which is creating
     *                 this expression.
     * @param opPos    The position of this iterator in the
     *                 opcode list from the compiler.
     * @param count    The insert position of the iterator.
     * @throws javax.xml.transform.TransformerException
     */
    protected void loadLocationPaths(Compiler compiler, int opPos, int count)
        throws javax.xml.transform.TransformerException {

        // TODO: Handle unwrapped FilterExpr
        int steptype = compiler.getOp(opPos);

        if (steptype == OpCodes.OP_LOCATIONPATH) {
            loadLocationPaths(compiler, compiler.getNextOpPos(opPos), count + 1);

            m_exprs[count] = createDTMIterator(compiler, opPos);
            m_exprs[count].exprSetParent(this);
        } else {

            // Have to check for unwrapped functions, which the LocPathIterator
            // doesn't handle.
            switch (steptype) {
                case OpCodes.OP_VARIABLE:
                case OpCodes.OP_EXTFUNCTION:
                case OpCodes.OP_FUNCTION:
                case OpCodes.OP_GROUP:
                    loadLocationPaths(compiler, compiler.getNextOpPos(opPos), count + 1);

                    WalkingIterator iter =
                        new WalkingIterator(compiler.getNamespaceContext());
                    iter.exprSetParent(this);

                    if (compiler.getLocationPathDepth() <= 0)
                        iter.setIsTopLevel(true);

                    iter.m_firstWalker = new wx.xml.xalan.xpath.axes.FilterExprWalker(iter);

                    iter.m_firstWalker.init(compiler, opPos, steptype);

                    m_exprs[count] = iter;
                    break;
                default:
                    m_exprs = new LocPathIterator[count];
            }
        }
    }

    /**
     * Returns the next node in the set and advances the position of the
     * iterator in the set. After a DTMIterator is created, the first call
     * to nextNode() returns the first node in the set.
     *
     * @return The next <code>Node</code> in the set being iterated over, or
     * <code>null</code> if there are no more members in that set.
     */
    public int nextNode() {
        if (m_foundLast)
            return DTM.NULL;

        // Loop through the iterators getting the current fetched
        // node, and get the earliest occuring in document order
        int earliestNode = DTM.NULL;

        if (null != m_iterators) {
            int n            = m_iterators.length;
            int iteratorUsed = -1;

            for (int i = 0; i < n; i++) {
                int node = m_iterators[i].getCurrentNode();

                if (DTM.NULL == node)
                    continue;
                else if (DTM.NULL == earliestNode) {
                    iteratorUsed = i;
                    earliestNode = node;
                } else {
                    if (node == earliestNode) {

                        // Found a duplicate, so skip past it.
                        m_iterators[i].nextNode();
                    } else {
                        DTM dtm = getDTM(node);

                        if (dtm.isNodeAfter(node, earliestNode)) {
                            iteratorUsed = i;
                            earliestNode = node;
                        }
                    }
                }
            }

            if (DTM.NULL != earliestNode) {
                m_iterators[iteratorUsed].nextNode();

                incrementCurrentPos();
            } else
                m_foundLast = true;
        }

        m_lastFetched = earliestNode;

        return earliestNode;
    }

    /**
     * This function is used to fixup variables from QNames to stack frame
     * indexes at stylesheet build time.
     *
     * @param vars List of QNames that correspond to variables.  This list
     *             should be searched backwards for the first qualified name that
     *             corresponds to the variable reference qname.  The position of the
     *             QName in the vector from the start of the vector will be its position
     *             in the stack frame (but variables above the globalsTop value will need
     *             to be offset to the current stack frame).
     */
    public void fixupVariables(java.util.Vector vars, int globalsSize) {
        for (int i = 0; i < m_exprs.length; i++) {
            m_exprs[i].fixupVariables(vars, globalsSize);
        }

    }

    /**
     * Returns the axis being iterated, if it is known.
     *
     * @return Axis.CHILD, etc., or -1 if the axis is not known or is of multiple
     * types.
     */
    public int getAxis() {
        // Could be smarter.
        return -1;
    }

    /**
     * @see wx.xml.xalan.xpath.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)
     */
    public void callVisitors(ExpressionOwner owner, XPathVisitor visitor) {
        if (visitor.visitUnionPath(owner, this)) {
            if (null != m_exprs) {
                int n = m_exprs.length;
                for (int i = 0; i < n; i++) {
                    m_exprs[i].callVisitors(new iterOwner(i), visitor);
                }
            }
        }
    }

    /**
     * @see Expression#deepEquals(Expression)
     */
    public boolean deepEquals(Expression expr) {
        if (!super.deepEquals(expr))
            return false;

        UnionPathIterator upi = (UnionPathIterator) expr;

        if (null != m_exprs) {
            int n = m_exprs.length;

            if ((null == upi.m_exprs) || (upi.m_exprs.length != n))
                return false;

            for (int i = 0; i < n; i++) {
                if (!m_exprs[i].deepEquals(upi.m_exprs[i]))
                    return false;
            }
        } else if (null != upi.m_exprs) {
            return false;
        }

        return true;
    }

    class iterOwner implements ExpressionOwner {
        int m_index;

        iterOwner(int index) {
            m_index = index;
        }

        /**
         * @see ExpressionOwner#getExpression()
         */
        public Expression getExpression() {
            return m_exprs[m_index];
        }

        /**
         * @see ExpressionOwner#setExpression(Expression)
         */
        public void setExpression(Expression exp) {

            if (!(exp instanceof LocPathIterator)) {
                // Yuck.  Need FilterExprIter.  Or make it so m_exprs can be just
                // plain expressions?
                WalkingIterator  wi  = new WalkingIterator(getPrefixResolver());
                FilterExprWalker few = new FilterExprWalker(wi);
                wi.setFirstWalker(few);
                few.setInnerExpression(exp);
                wi.exprSetParent(UnionPathIterator.this);
                few.exprSetParent(wi);
                exp.exprSetParent(few);
                exp = wi;
            } else
                exp.exprSetParent(UnionPathIterator.this);
            m_exprs[m_index] = (LocPathIterator) exp;
        }

    }


}
